Methods and apparatuses for removing thermal energy from a nuclear reactor

ABSTRACT

Method and apparatuses are provided for removing thermal energy from a nuclear reactor, which are fault tolerant. The apparatus includes at least one heat pipe configured to absorb thermal energy produced by the nuclear reactor. In addition, the apparatus includes a first compartment thermally coupled to the at least one heat pipe. The first compartment is configured to contain a first gas. Furthermore, the apparatus includes a second compartment thermally coupled to the at least one heat pipe. The second compartment is configured to contain a second gas and configured to isolate the second gas from the first gas.

RELATED APPLICATION

This application is a Divisional of application Ser. No. 10/405,000filed Mar. 31, 2003, now U.S. Pat. No. 6,768,781.

TECHNICAL FIELD

The present invention generally relates to methods and apparatuses forremoving thermal energy from a nuclear reactor, and more particularlyrelates to methods and apparatuses for removing thermal energy from anuclear reactor, which are fault tolerant.

BACKGROUND

A nuclear reactor produces thermal energy (i.e., heat) by fissioning afissile material, which is typically fabricated into fuel elements andassembled into a nuclear core. In a gas cooled nuclear reactor, thethermal energy produced by the fuel elements is transferred to a gas,which is preferably an inert gas. The heated gas is subsequentlycirculated through an energy conversion system that uses the heated gasto generate power, such as electrical power. The energy conversionsystem of the nuclear reactor can implement any number of energyconversion cycles, such as a Rankine cycle or a Brayton cycle.

Gas cooled nuclear reactors that use Rankine, Brayton or other energyconversion cycles provide an abundant source of energy for numerousapplications. For example, these gas cooled nuclear reactors arepreferable energy sources for spacecraft, including energy sources forpropulsion and onboard applications of spacecraft. However, current gascooled nuclear reactor designs for spacecraft and other vehicle ornon-vehicle applications are subject to single point failures, which areundesirable in most, if not all situations.

For example, one single point failure, which current gas cooled nuclearreactor designs are susceptible, is a gas leak. A gas leak in the gascooled nuclear reactor generally results in a loss of coolant. The lossof coolant typically results in an overheating of the reactor.Therefore, a gas leak can ultimately result in a reactor shutdown andremoval of the energy source.

Accordingly, it is desirable to provide methods for removing thermalenergy from a nuclear reactor that includes redundancy to address one ormore gas leaks (i.e., methods for removing thermal energy from a nuclearreactor that are fault tolerant). In addition, it is desirable toprovide apparatuses for removing thermal energy from a nuclear reactorthat includes redundancy to address one or more gas leaks (i.e.,apparatuses for removing thermal energy from a nuclear reactor that arefault tolerant). Furthermore, other desirable features andcharacteristics of the present invention will become apparent from thesubsequent summary, detailed description, and the appended claims, takenin conjunction with the accompanying drawings and the foregoingtechnical field and background.

BRIEF SUMMARY

An apparatus is provided for removing thermal energy from a nuclearreactor that is fault tolerant. The apparatus includes at least one heatpipe configured to absorb thermal energy produced by the nuclearreactor. In addition, the apparatus includes a first compartmentthermally coupled to the at least one heat pipe. The first compartmentis configured to contain a first gas. Furthermore, the apparatusincludes a second compartment thermally coupled to the at least one heatpipe. The second compartment is configured to contain a second gas andconfigured to isolate the second gas from the first gas.

A method is provided for removing thermal energy from a nuclear reactorthat is fault tolerant. The method includes the steps of absorbingthermal energy produced by the nuclear reactor and transferring at leasta first portion of the thermal energy to a first compartment andtransferring at least a second portion of the thermal energy to a secondcompartment. The method further includes the steps of introducing afirst gas into the first compartment and a second gas into the secondcompartment and isolating the second gas introduced into the secondcompartment from the first gas introduced into the first compartment.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe following drawing figures, wherein like numerals denote likeelements, and:

FIG. 1 is a vehicle having an apparatus for removing thermal energy froma nuclear reactor in accordance with an exemplary embodiment of thepresent invention;

FIG. 2 is a simplified schematic of the apparatus for removing thermalenergy from the nuclear reactor of FIG. 1 in accordance with anexemplary embodiment of the present invention;

FIG. 3 is a heat pipe of the apparatus for removing thermal energy fromthe nuclear reactor of FIG. 2 in accordance with an exemplary embodimentof the present invention;

FIG. 4 is a cross-sectional view of the heat pipe of FIG. 3 taken alonglines 4—4;

FIG. 5 is the energy conversion system of FIG. 1 in accordance with anexemplary embodiment of the present invention; and

FIG. 6 is one of the energy conversion subsystems of FIG. 5 in greaterdetail in accordance with the present invention.

DETAILED DESCRIPTION

The following detailed description of the invention is merely exemplaryin nature and is not intended to limit the invention or the applicationand uses of the invention. Furthermore, there is no intention to bebound by any expressed or implied theory presented in the precedingtechnical field, background, or summary, or the following detaileddescription or accompanying drawings.

Referring to FIG. 1, a vehicle 20 is illustrated that includes a nuclearreactor 22, a radiation shield 23 and an apparatus 24 for removingthermal energy (e.g., heat) from the nuclear reactor 22. In accordancewith one exemplary embodiment, the vehicle 20 is a spacecraft. However,it should be understood that any number of land, water, air or spacevehicles can utilize the apparatus 24 for removing thermal energy fromthe nuclear reactor 22. In addition, the apparatus 24 can be used forremoving thermal energy from a nuclear reactor in a non-vehicleapplication. Furthermore, corresponding methods for removing thermalenergy from a nuclear reactor in vehicle and non-vehicle applicationsare evident from the following description of the apparatus 24.

The nuclear reactor 22 is configured to generate thermal energy usingany number of techniques known to those of ordinary skill in the art,such as nuclear fission (i.e., fissioning a fissile material). Theapparatus 24 is thermally coupled to the nuclear reactor 22 andconfigured to remove at least a portion of the thermal energy generatedby the nuclear reactor 22. An energy conversion system 26 is coupled tothe apparatus 24 and configured to convert at least a portion of thethermal energy removed from the nuclear reactor 22 into power, such aselectrical power. The energy conversion system 26 is preferably coupledto one or more systems of the vehicle 20 in order to supply at leastsome of the power for use by the one or more systems. For example, theenergy conversion system 26 can be coupled to a propulsion system (e.g.,electric thrusters (28,30)), life support system 32, communicationsystem 34, guidance system 36, and/or navigation system 38, or the like.However, the energy conversion system 26 can be coupled to any number ofindividual devices or a collection of devices that can be configured toutilize the power produced from the thermal energy originally generatedby the nuclear reactor 22 and removed by the apparatus 24.

Referring to FIG. 2, a perspective view of the apparatus 24 isillustrated in accordance with an exemplary embodiment of the presentinvention. Generally, the apparatus 24 has multiple compartments(40,42,44,46,48) and at least one heat pipe 50 that is thermally coupledto the one or more of the compartments (40,42,44,46,48). Preferably, theapparatus 24 includes multiple heat pipes 50 that are thermally coupledto one or more of the compartments (40,42,44,46,48) and the one or moreheat pipes 50 are configured to absorb at least a portion of the thermalenergy produced by the nuclear reactor and transfer at least a portionof this absorbed thermal energy into one or more of the compartments(40,42,44,46,48).

Referring to FIG. 3 and FIG. 4, a heat pipe 50 is illustrated inaccordance with an exemplary embodiment of the present invention.Preferably, the heat pipe 50 is an annular heat pipe that is preferablyformed of thermally conductive material. The heat pipe 50 is configuredto enclose one or more nuclear fuel pins 54 of the nuclear reactor,which are composed of any number of nuclear materials such as uranium,plutonium, uranium nitride, uranium oxide or the like. The annular ofthe heat pipe 50 shape can be any number of ellipses, including a circleas shown in FIG. 4, or the pipe can have a non-annular configuration,such as a pipe with a triangular, rectangular, pentagonal, or hexagonalconfiguration, or the like.

Preferably, the heat pipe 50 includes an inner pipe 52 enclosing thenuclear fuel 54, an outer pipe 56 enclosing the inner pipe 52, and aspace 58 interposed between the inner pipe 52 and the outer pipe 56.Preferably, the space 58 is a vapor space that contains a fluid and theouter pipe 56 has one or more protrusions, ribs or fins 60. The fluidwithin the space 58 can be any number of gases or liquids and the one ormore protrusions, ribs or fins 60 preferably extend from the outer pipe56 and one or more protrusions, ribs or fins 60 preferably exists foreach of the compartments in thermal contact with the heat pipe(s). Thefluid in the space 58 and/or the one or more protrusions, ribs or fins60 enhances the transfer of thermal energy from the nuclear fuel to theseparate environment or environments surrounding the heat pipe, which inthe present invention is the one or more of the compartments(40,42,44,46,48) as shown in FIG. 2.

Referring to FIG. 2, the apparatus 24 is shown with five compartments(e.g., a first compartment 40, a second compartment 42, a thirdcompartment 44, a fourth compartment 46, and a fifth compartment 48)that provide five separate environments surrounding the heat pipes 50.However, the apparatus 24 can have fewer than five compartments andgreater than five compartments. At least the first compartment 40 andthe second compartment 42 are thermally coupled to at least one of theheat pipes 50 and more preferably thermally coupled to substantially allor all of the heat pipes 50. Even more preferably, each of the firstcompartment 40, second compartment 42, third compartment 44, fourthcompartment 46 and fifth compartment 48 are thermally coupled to atleast one of the heat pipes 50 and most preferably each of the each ofthe first compartment 40, second compartment 42, third compartment 44,fourth compartment 46 and fifth compartment 48 are thermally coupled tosubstantially all or all of the heat pipes 50.

At least the first compartment 40 and second compartment 42 areconfigured to contain a first gas and a second gas, respectively.Furthermore, if the apparatus 24 has additional compartments, such asthe third compartment 44, fourth compartment 46, fifth compartment 48,or other compartments, each of these additional compartments arepreferably configured to contain a gas. For example, the thirdcompartment 44, fourth compartment 46 and fifth compartment 48 can beconfigured to contain a third gas, fourth gas, and a fifth gas,respectively.

Each of these gases in the compartments (40,42,44,46,48) can be anynumber of gases, and each of the gases is preferably an inert gas. Forexample, the gas of one or more of the compartments can be helium orargon. Each of the gases in each of the compartments can be the same orsimilar type of gas or each of the gases in each of the compartment canbe a different type of gas.

In addition to containment of a gas, at least two or the compartments,preferably more than two of the compartments, and more preferably eachof the compartments (40,42,44,46,48) are configured to isolate the gascontained in the respective compartment. As used herein, a structure isconfigured to isolate a gas from another gas in another structure if thegas cannot enter the structure with the other gas. Therefore, acompartment is configured to isolate a gas from another gas in anothercompartment if the gas cannot enter the compartment with the other gasFor example, the second compartment 42 is configured to at least isolatethe second gas from the first gas contained in the first compartment 40and also preferably configured to isolate the second gas from the gasescontained in the third compartment 44, fourth compartment 46, and fifthcompartment 48. In addition, each of the gases contained in each of thecompartments are isolated from the other gases contained in the othercompartments. This isolation of the gases in each of the compartmentsprovides redundancy in the apparatus 24 for removing thermal energy fromthe nuclear reactor, as a gas leak in one or more of the compartmentdoes not result in a complete gas loss of the apparatus 24. Furthermore,at least a portion of the thermal energy previously removed by the gasin a leaking compartment is distributed to non-leaking compartments inaccordance with the present invention through one or more of the heatpipes 50 and adjoining walls of the compartments (40,42,44,46,48).

The gas in each of the compartments (40,42,44,46,48) is preferablyreceived through an inlet duct (62,64,66,68,70) associated with one ofthe compartments (40,42,44,46,48). With particular reference to thefirst compartment 40 as an illustrative example, the gas flows from theinlet duct 62 into the first compartment 40. As the gas flows throughthe first compartment 40, contact is made with the heat pipes 50extending into the first compartment 40 and the thermal energy absorbedby the heat pipes 50 is transferred to the gas, thereby heating the gas.The heated gas exists through an outlet duct 72 associated with thefirst compartment 40, where it is preferably converted to power by anenergy conversion system.

Referring to FIG. 5, the energy conversion system 26 is illustrated inadditional detail in accordance with an exemplary embodiment of thepresent invention. The energy conversion system 26 preferably includesmultiple energy conversion subsystems (74,76,78,80,82), with the energyconversion subsystems configured to receive the heated gas and use theheated gas to generate power, such as electrical power. Preferably, asingle energy conversion sub-system is associated with each of thecompartments in order to maintain the isolation of the gases. However, asingle energy conversion sub-system can be configured to receive theheated gases from more than one compartment, thereby maintainingisolation of gases in the compartments associated with the single energyconversion sub-system.

Referring to FIG. 6, one of the energy conversion sub-systems 74 of FIG.5 is illustrated in greater detail. Each of the subsystems can have theconfiguration shown in FIG. 6, or one or more of the sub-systems canhave a different energy conversion configuration. In this illustrativeexample, the energy conversion subsystem 74 implements a Brayton energyconversion cycle. However, other energy conversion cycles can beimplemented in accordance with the present invention, including but notlimited to a Rankine energy conversion cycle.

Generally, the Brayton energy conversion cycle is conducted with acompressor turbine 84, work turbine 86, heat exchanger 88 and compressor90. Initially, the heated gas exiting the outlet conduit passes throughthe compressor turbine 84 and subsequently passes through the workturbine 86. The compressor turbine 84 is mechanically coupled to thecompressor 90 and generally provides the powering force to operate thecompressor 90. The work turbine 86 rotates a turbine shaft, which isconnected to any number of mechanisms that generate power, such as anelectrical power generator 92, as known to those of ordinary skill inthe art. After the heated gas passes through the compressor turbine 84and work turbine 86, it is preferably thermally conditioned by the heatexchanger 88. For example, the temperature of the gas exiting theturbines (84,86) is reduced by the heat exchanger 88. The gas exitingthe heat exchanger 88 is compressed and passed to the inlet conduit ofthe apparatus for thermal conditioning (i.e., heating) of the gas by thereactor, and the cycle repeats.

This well known cycle and the mechanical elements performing the Braytoncycle can be implemented with any number of mechanisms and variations toproduce an abundant source of energy for numerous applications,including vehicle and non-vehicle applications, with the thermal energyremoved from the nuclear reactor with the apparatus of the presentinvention. (See U.S. Pat. No. 3,663,364 as issued to Thompson et al onMay 16, 1972 and U.S. Pat. No. 4,057,465 as issued to Thompson et al onNov. 8, 1997 for additional descriptions of the flow loop, which areboth hereby incorporated in their entirety by reference.) Alternatively,other energy conversion cycles can be used to generate power with thethermal energy removed from the nuclear reactor of the presentinvention. Nevertheless, the apparatuses and corresponding methods ofthe present invention increase energy source reliability as a gas leakwill result in an isolated loss of gas that does not significantlyreduce the gas that is available for removal of thermal energy from thereactor. Accordingly, a gas leak will not typically result in anoverheating of the nuclear reactor and the ultimate shutdown of thereactor as the remaining non-leaking compartments provide the gas toadequately remove the thermal energy from the nuclear reactor.

While at least one exemplary embodiment has been presented in theforegoing detailed description of the invention, it should beappreciated that a vast number of variations exist. It should also beappreciated that the exemplary embodiment or exemplary embodiments areonly examples, and are not intended to limit the scope, applicability,or configuration of the invention in any way. Rather, the foregoingdetailed description will provide those skilled in the art with aconvenient road map for implementing an exemplary embodiment of theinvention. It being understood that various changes may be made in thefunction and arrangement of elements described in an exemplaryembodiment without departing from the scope of the invention as setforth in the appended claims.

1. A method for removing thermal energy from a nuclear reactor,comprising the steps of: absorbing thermal energy produced by thenuclear reactor; transferring at least a first portion of the thermalenergy to a first compartment coupled to a first gas inlet and a firstgas outlet; transferring at least a second portion of the thermal energyto a second compartment coupled to a second gas inlet and a second gasoutlet; introducing a first gas into said first compartment, said firstgas inlet and said first gas outlet and a second gas into said secondcompartment, said second gas inlet and said second gas outlet; andpneumatically isolating said second gas introduced into said secondcompartment, said second as inlet and said second gas outlet from saidfirst gas introduced into said first compartment, said first gas inletand said first gas outlet.
 2. The method for removing thermal energyfrom the nuclear reactor of claim 1, further comprising the steps of:transferring at least a third portion of the thermal energy to a thirdcompartment coupled to a third gas inlet and a third gas outlet;introducing a third gas into said third compartment, said third gasinlet and said third gas outlet; and pneumatically isolating said thirdgas introduced into said third compartment, said third gas inlet andsaid third gas outlet from said first gas introduced into said firstcompartment, said first gas inlet and said first as outlet.
 3. Themethod for removing thermal energy from the nuclear reactor of claim 2,further comprising the step of pneumatically isolating said third gasintroduced into said third compartment, said third gas inlet and saidthird gas outlet from said second gas introduced into said secondcompartment, said second gas inlet and said second gas outlet.
 4. Themethod for removing thermal energy from the nuclear reactor of claim 2,further comprising the steps of: transferring at least a fourth portionof the thermal energy to a fourth compartment coupled to a fourth gasinlet and said fourth gas outlet; introducing a fourth gas into saidfourth compartment, said fourth gas inlet and said fourth gas outlet;and pneumatically isolating said fourth gas introduced into said fourthcompartment, said fourth gas inlet and said fourth gas outlet from saidfirst gas introduced into said first compartment, said first gas inletand said first gas outlet.
 5. The method for apparatus for removingthermal energy from the nuclear reactor of claim 4, further comprisingthe steps of pneumatically isolating said fourth gas introduced intosaid fourth compartment, said fourth gas inlet and said fourth gasoutlet from said second gas introduced into said second compartment,said second gas inlet and said second gas outlet and said third gasintroduced into said third compartment, said third gas inlet and saidthird gas outlet.
 6. The method for removing thermal energy from thenuclear reactor of claim 4, further comprising the steps of:transferring at least a fifth portion of the thermal energy to a fifthcompartment coupled to a fifth gas inlet and a fifth gas outlet;introducing a fifth gas into said fifth compartment, said fifth gasinlet and said fifth gas outlet; and pneumatically isolating said fifthgas introduced into said fifth compartment, said fifth gas inlet andsaid fifth gas outlet from said first gas introduced into said firstcompartment, said fourth gas inlet and said first gas outlet.
 7. Themethod for apparatus for removing thermal energy from the nuclearreactor of claim 6, further comprising the steps of pneumaticallyisolating said fifth gas introduced into said fifth compartment, saidfifth gas inlet and said fifth gas outlet from said second gasintroduced into said second compartment, said second gas inlet and saidsecond gas outlet, said third gas introduced into said thirdcompartment, said third gas inlet and said third gas outlet, and saidfourth gas introduced into said fourth compartment, said fourth gasinlet and said fourth gas outlet.